Cyclic C${}_4^{+}$ as the carrier of the diffuse interstellar band at 503.9 nm?

Serge. A. Krasnokutski, Lisa Ganner, Milan Ončák +5

The diffuse interstellar bands (DIBs) have remained a mystery in astronomy since their discovery over a century ago. The only currently known carrier is C${}_{60}^{+}$ responsible for…